diff --git a/services/hermes/scripts/claude_oauth_broker.py b/services/hermes/scripts/claude_oauth_broker.py
index 2718f97f..f0eeca4c 100644
--- a/services/hermes/scripts/claude_oauth_broker.py
+++ b/services/hermes/scripts/claude_oauth_broker.py
@@ -67,11 +67,6 @@ _auth_probe_value: dict[str, Any] = {}
 HEALTH_POLL_SECONDS: Final = max(
     30, int(os.environ.get("HERMES_CLAUDE_HEALTH_POLL_SECONDS", "60"))
 )
-AUTH_PROBE_GRACE_SECONDS: Final = max(
-    60, int(os.environ.get("HERMES_CLAUDE_AUTH_PROBE_GRACE_SECONDS", "300"))
-)
-
-
 def _read_secret(file_env_name: str) -> str:
     """Read a secret only from its runtime-mounted file."""
     path = os.environ.get(file_env_name, "").strip()
@@ -296,32 +291,28 @@ def _subscription_health(force: bool = False) -> dict[str, Any]:
         )
         api_provider = raw.get("apiProvider") if isinstance(raw, dict) else None
         auth_method = raw.get("authMethod") if isinstance(raw, dict) else None
-        # A concurrent inference can make Claude's secondary auth-status
-        # process time out or return no JSON. A real, recent inference is
-        # stronger evidence than that inconclusive probe. Preserve the last
-        # proven-good auth state briefly, but never mask an explicit logged-out
-        # response from the CLI.
-        recent_success = False
-        try:
-            last_success = datetime.fromisoformat(
-                str(previous.get("last_success_at") or "").replace("Z", "+00:00")
+        # Cold starts and concurrent inference can make Claude's secondary
+        # auth-status process time out or return no JSON. Once this broker has
+        # proven first-party access, only an explicit logged-out response or an
+        # authoritative inference auth failure may revoke that evidence.
+        # Otherwise periodic probe timeouts would repeatedly eject a working
+        # subscription from routing.
+        known_authenticated = bool(
+            (
+                previous.get("authenticated") is True
+                and previous.get("api_provider") == "firstParty"
             )
-            if last_success.tzinfo is None:
-                last_success = last_success.replace(tzinfo=timezone.utc)
-            age = (checked_time - last_success.astimezone(timezone.utc)).total_seconds()
-            recent_success = 0 <= age <= AUTH_PROBE_GRACE_SECONDS
-        except (TypeError, ValueError):
-            pass
+            or previous.get("last_authenticated_at")
+            or previous.get("last_success_at")
+        )
         probe_stale = bool(
             not probe_conclusive
-            and recent_success
-            and previous.get("authenticated") is True
-            and previous.get("api_provider") == "firstParty"
+            and known_authenticated
         )
         if probe_stale:
             authenticated = True
-            api_provider = previous.get("api_provider")
-            auth_method = previous.get("auth_method")
+            api_provider = previous.get("api_provider") or "firstParty"
+            auth_method = previous.get("auth_method") or "oauth_token"
         value = {
             "transport": "claude-code-cli-subscription",
             "state": "available" if authenticated else "unavailable",
@@ -332,8 +323,16 @@ def _subscription_health(force: bool = False) -> dict[str, Any]:
             "auth_probe_stale": probe_stale,
             "subscription_type": raw.get("subscriptionType")
             if isinstance(raw, dict)
-            else None,
+            else previous.get("subscription_type"),
         }
+        if authenticated:
+            value["last_authenticated_at"] = (
+                checked_at
+                if probe_conclusive
+                else previous.get("last_authenticated_at")
+                or previous.get("last_success_at")
+                or checked_at
+            )
         # Readiness probes must not erase the most recently observed native
         # usage window or successful route metadata. They only refresh auth.
         for key in (
@@ -447,6 +446,11 @@ def _invoke(payload: dict[str, Any]) -> tuple[dict[str, Any], dict[str, int], st
     health.update(
         {
             "state": "available",
+            "authenticated": True,
+            "api_provider": "firstParty",
+            "auth_method": "oauth_token",
+            "auth_probe_stale": False,
+            "last_authenticated_at": datetime.now(timezone.utc).isoformat(),
             "last_success_at": datetime.now(timezone.utc).isoformat(),
             "latency_ms": int((time.monotonic() - started) * 1000),
             "model": actual_model,
diff --git a/testing/tests/test_hermes_claude_broker.py b/testing/tests/test_hermes_claude_broker.py
index 1f9fb7a9..5e29a105 100644
--- a/testing/tests/test_hermes_claude_broker.py
+++ b/testing/tests/test_hermes_claude_broker.py
@@ -154,6 +154,36 @@ def test_transient_auth_probe_keeps_recent_proven_access(monkeypatch, tmp_path)
     assert health["auth_probe_stale"] is True
 
 
+def test_transient_auth_probe_keeps_older_proven_access(monkeypatch, tmp_path) -> None:
+    module = _module(monkeypatch)
+    module.HEALTH_PATH = tmp_path / "claude.json"
+    module.HEALTH_PATH.write_text(
+        json.dumps(
+            {
+                "authenticated": False,
+                "last_success_at": "2026-01-01T00:00:00+00:00",
+            }
+        ),
+        encoding="utf-8",
+    )
+    monkeypatch.setattr(
+        module.subprocess,
+        "run",
+        lambda *_args, **_kwargs: SimpleNamespace(
+            returncode=1, stdout="", stderr="transient timeout"
+        ),
+    )
+
+    health = module._subscription_health(force=True)
+
+    assert health["authenticated"] is True
+    assert health["state"] == "available"
+    assert health["api_provider"] == "firstParty"
+    assert health["auth_method"] == "oauth_token"
+    assert health["auth_probe_stale"] is True
+    assert health["last_authenticated_at"] == "2026-01-01T00:00:00+00:00"
+
+
 def test_explicit_logged_out_probe_clears_recent_access(monkeypatch, tmp_path) -> None:
     module = _module(monkeypatch)
     module.HEALTH_PATH = tmp_path / "claude.json"
@@ -183,3 +213,4 @@ def test_explicit_logged_out_probe_clears_recent_access(monkeypatch, tmp_path) -
     assert health["authenticated"] is False
     assert health["state"] == "unavailable"
     assert health["auth_probe_stale"] is False
+    assert "last_authenticated_at" not in health